They never asked. 

That appears to be Sen. Roland Burris' rationale for omitting key details last month about conversations he had with aides to former Illinois Gov. Rod Blagojevich that preceded his surprise appointment to the U.S. Senate. 

State Republicans are calling for Burris to step down in light of revelations that he amended his testimony to the Illinois impeachment committee that weighed whether to oust Blagojevich.

Burris, who had been appointed by the governor in the waning days of his term to fill the seat vacated by President Obama, was a star witness in the probe into alleged pay-to-play activities.

The senator filed an affidavit with the panel on Feb. 5 noting that Blagojevich's brother, Rob Blagojevich, solicited him for donations to the governor's campaign before he was appointed, a point Burris never mentioned during his Jan. 8 testimony. 

But does the omission amount to perjury? 

A review of the testimony Burris gave to the House panel last month shows that if Burris didn't lie about the chain of events that led to his appointment, he certainly had numerous opportunities to clear the air. 

The most commonly cited opportunity came toward the beginning of his lengthy testimony. 

In that exchange, Republican state Rep. Jim Durkin asked Burris if he had "any conversations" with Blagojevich prior to the governor's arrest about his "desire to be appointed" to the Senate seat. 

"No," Burris said. 

Durkin followed up, asking if Burris talked to any "members of the governor's staff or anyone closely related to the governor, including family members or any lobbyists ... about your desire to seek the appointment prior to the governor's arrest." Durkin offered as examples the governor's brother, Rob Blagojevich, Blagojevich's former Chief of Staff John Harris, who was arrested in December with the governor, and other associates. 

After asking for "a moment" to consider the question, Burris said: "I talked to some friends about my desire to be appointed, yes." 

Durkin restated the question, and Burris briefly described a meeting he had with Lon Monk, the governor's former chief of staff. He said he brought up his interest in the seat. 

Finally, Durkin asked if he was "directly or indirectly aware of a quid pro quo with the governor" regarding the appointment. 

"No, sir," Burris said. He did not describe any conversations with Rob Blagojevich. 

But in his affidavit filed in early February, Burris clarified that the governor's brother called him three times starting in late October to "seek my assistance in fundraising" for the governor. He said in the affidavit, and later told reporters, that he refused to raise or donate any money since he was interested in a gubernatorial appointment to the Senate seat. 

Burris said Monday that there was "no change" in his testimony. He said he filed the affidavit only because when he reviewed the transcript he realized he "said 'yes' ... to all those names, but we had not addressed those names." 

At least one Republican says this omission amounts to perjury. 

"He lied. ... The question (from Durkin) couldn't have been any clearer," Illinois House Minority Leader Tom Cross told FOX News Monday. "He needs to step down." 

The transcript shows other opportunities when Burris could have brought up his conversations with the former governor's brother. 

-- About halfway into the testimony, Durkin asked Burris whether he'd made any contributions to the governor since July of last year. Burris said he had not, and that the last contribution was June 27. 

Durkin asked if Burris had thrown a fundraiser for the governor or had directed anybody to make contributions since July. Burris again said, "No." 

-- Later on in the testimony, Burris was asked to assure the panel that Burris had not "promised" anything to the governor as part of an exchange. 

"There was no conversation, none to that effect, and I know you answered this on numerous occasions, no quid pro quo, none of that?" asked Democratic Rep. Mary Flowers. 

"Absolutely, positively not," Burris said. 

-- Finally, Durkin asked Burris at one point in the questioning whether he exchanged any "writings or documents" with the governor or his staff regarding his qualifications or interest regarding the Senate seat. 

Burris said there was nothing in writing. 

But Burris clarified in his affidavit that he likely spoke to Doug Scofield and John Wyma -- two of the Blagojevich associates Durkin mentioned in his early questioning -- regarding his interest in the seat as far back as June. 

Burris told reporters Sunday that he is on the level, explaining that he followed the line of questioning whenever it went in another direction. 

"Let me say to you, as a witness on the stand, I was answering questions that were asked of me," he said. 

Burris said Monday that he was planning all along to file a supplement to his remarks, to fill in any blanks from the testimony. 

But Republicans say Burris should have disclosed the conversation earlier about a possible proposed quid pro quo with the governor's brother -- since the former governor landed in hot water over accusations that he tried to sell the seat that Burris wanted. 

"This entire process has been an embarrassment," Illinois GOP spokesman Lance Trover told FOXNews.com. "People have serious questions about the truthfulness of his testimony and what he told this committee." 

Jim Manley, spokesman for Senate Majority Leader Harry Reid, said Monday that, "clearly it would have been better if Senator Burris had provided this information when he first testified." 

He said Reid is "reviewing" the affidavit and will await action by Illinois legislators. 

FOXNews.com's Judson Berger and FOX News' Trish Turner contributed to this report.